1. Field
One embodiment of the invention relates to a fuel cell, and more particularly, to a method for maintaining an output of the fuel cell.
2. Description of the Related Art
Currently, a secondary battery, such as a lithium ion battery, is primarily used as a power source of an electronic device, such as a portable notebook personal computer, mobile equipment, and the like. In response to an increase in power consumption stemming from sophistication of functionality of an electronic device or a request for longer-duration usage of the electronic device, a high-power, recharge-free compact fuel cell has recently been expected as a new power source. Among various types of fuel cells that are available, a direct methanol fuel cell (hereinafter abbreviated as “DMFC”) using a methanol solution as a fuel is better than a fuel cell using hydrogen as a fuel in terms of ease of handling a fuel, and a system for DMFC is simple. Since the DMFC can reuse unused fuel discharged during power generation for power generation, DMFC is suitable for use as a power source of a compact electronic device required to operate for a long period of time.
In the DMFC, chemical reaction for power generation is induced at the cathode of stacks by acquisition of air and hence is susceptible to the influence of impurities in the air. JP-A-2006-85971 discloses a fuel cell device having a dust-collection filter disposed at least at one of an air intake, an air intake passage from the air intake to an air-supply pump, and an air-supply passage from an outlet port of the air-supply pump to an air supply port of a fuel-cell power generation section. Dust is eliminated from the air supplied to the power generation section of the fuel-cell power device by means of the dust-collection filter. Hence, a decrease in power-generation performance or a decrease in the life of a battery, which would otherwise be caused as a result of adhesion of dust to an air flow passage or a proton exchange membrane, can be prevented.
However, the above technique has a problem of a failure to prevent intrusion of small dust, or the like, which cannot be caught by the dust-collection filter. For this reason, there may often arise a case where a reaction area is reduced by impurities, such as dust or the like, adhering to the surface of the cathode, resulting in a drop in output.